A Massachusetts man is headed to prison for the fatal stabbing of his teenage girlfriend.

Nickolas Lacrosse, of Springfield, was sentenced to life without parole Thursday after a jury found him guilty of first-degree murder.

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Prosecutors say Lacrosse stabbed 17-year-old Kathryn Mauke 32 times in her own home in February 2015 because he was angry she had broken up with him.

"But 32 blows were necessary to end Kathryn's life," Assistant District Attorney Mary Sandstrom said in her closing argument, according to Mass Live. "He wanted her dead. He wanted to make sure of it."

PEOPLE reports that Mauke broke up with Lacrosse a month before her murder, and by the time she was killed, had begun dating someone else.

The now-23-year-old Lacrosse previously testified that he didn’t intend to kill Mauke but went to her home to get “clarification” on the break-up.

According to Mass Live, Mariah Mauke recalled finding her big sister's body on the kitchen floor the day she was killed.

"And from there everything's been a blur," she said.

Two defense experts had testified that Lacrosse didn’t have the ability to control his actions.

Members of a Hampden Superior Court jury found Lacrosse guilty Wednesday after a trial that lasted about three weeks.

The victim's sister, Ashley Ballou-Mauke, described Kathryn Mauke as her "teacher and protector."

"When I wake in the morning, the sun doesn't seem to shine as brightly as it once did,"her father, Daniel Mauke, said. "Trying to focus on the present and future has become difficult."